1. Field of the Invention
The invention relates to a vehicle occupant protection system having a child seat for a motor vehicle including a firing circuit with a firing cap for an airbag unit, a control unit for activating the firing cap, a lockable latching device for attaching a child seat, and a sensor device which prevents the firing cap from being activated when the latching device is locked.
In terms of vehicle occupant protection in motor vehicles, the protection of children traveling in vehicles, in particular small children, is also very important. Child seats have been developed that can be attached to the front passenger seat facing backward with respect to the direction of travel so that a child sitting on the child seat is located near to the mother or father who is driving the vehicle, but in the event of an impact of the vehicle is still protected in particular by the backrest of the child seat itself. A problem that occurs with such a child seat is that an airbag located in front of the front passenger seat must not be allowed to trigger when the child seat is located on the front passenger seat. Triggering of the airbag could constitute an additional risk of injury for the child.
In order to solve this problem, the genus-forming U.S. Pat. No. 5,468,014 issued to Gimbel et al., on which the appended FIG. 4 is largely based, proposes that a sensor should be used to determine whether or that a child seat is attached to a lockable latching device and to deactivate the triggering of the airbag assigned to the front passenger seat when the latching device is locked. According to FIG. 4, latching devices 6 for receiving attachment components 10 formed on a child seat 8 are provided on a front passenger seat 2 in the rear-most region of its seat cushions 4. The latching devices 6 are rigidly connected to the frame of the front passenger seat 2, and the attachment components 10 are rigidly connected to a base frame of the child seat 8, which is embodied as a safety seat. According to Gimbel et al., sensors (not illustrated) are disposed in the latching devices 6 and are connected via lines 12 to a control unit 14 (electronic control unit). The control unit 14 actuates an airbag unit 16, which is accommodated in the region in front of the front passenger seat 2 in the dashboard 18 of the motor vehicle. The sensors (not illustrated), which are accommodated in the latching devices 6, may be embodied, for example, as pulse transmitters. The control unit 14 reacts to pulses generated by the pulse transmitters and blocks triggering of the airbag unit 16. Furthermore, the sensors may be embodied in such a way that when the attachment components 10 are not satisfactorily latched to the latching devices 6, they emit a signal that triggers a warning indicator in the dashboard.
Another possible way of generating a signal for deactivating the airbag is to accommodate transceiver mats in the front passenger seat 2 and to accommodate in the child seat 8 a transponder that reacts to a transmitted signal with a response signal which is then transmitted from the reception mat to the control unit 14 and triggers blocking of the airbag.
It is accordingly an object of the invention to provide a vehicle occupant protection system having a child seat for a motor vehicle that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that obtains a particularly high degree of protection against malfunctions in a simple construction.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a vehicle occupant protection system for a motor vehicle includes a firing circuit, a control unit, a lockable latching device, and a sensor device. The firing circuit includes a firing cap for an airbag unit. The control unit activates the firing cap. The lockable latching device attaches a child seat. The sensor device has a switch and an electrical element connected in parallel to one another. The switch is open when the latching device is locked to prevent the firing cap from being activated. Preferably, the electrical element is a resistor. The control unit can determine an electrical resistance of the firing circuit. This is very useful when the vehicle occupant protection system includes a series of switches, each with a respective resistor connected in parallel to the second switch, because by judging the overall resistance the control unit can determine if all of the switches have been activated. The switch can include a Reed contact. The Reed contact is opened by a magnet that is positioned when the child seat is installed.
In the vehicle occupant protection system according to the invention, actuating the switch influences the effectiveness of the electrical functional element. The switch influences the trip circuit to prevent the functional element that is then electrically active from triggering the airbag.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a vehicle occupant protection system having a child seat for a motor vehicle, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.